Heart failure, also known as congestive heart failure, is a leading cause of cardiovascular disease-related death. Heart failure is an abnormality of cardiac function in which cardiac output is not able to meet the needs of peripheral tissue. The early detection of heart failure is often difficult because of the many underlying causes, such as ischemic heart disease (coronary artery disease), hypertension (high blood pressure), and diabetes. Because the causes of heart failure are varied, the onset can be subtle (e.g., without overt symptoms) and difficult for a patient to recognize. As a result, the patient may alter his or her daily activities rather than making an appointment to be evaluated by his physician. When symptoms are missed, the patient faces an increased risk of an acute decompensated heart-failure event that requires hospitalization.
An implantable or other ambulatory medical device can be used to monitor a physiological condition of a patient, such as a patient at risk for a worsening heart failure condition. For example, a cardiac function management device, such as an implantable pacemaker, cardioverter-defibrillator, or a cardiac resychronization device can be implanted into or otherwise provided to a patient. The cardiac function management device can be used treat the patient's cardiac condition. For example, it can be configured to deliver electrical stimulation or other therapy. Such devices can be used for internal or other ambulatory monitoring of the patient's condition such as to aid in diagnosis. The devices can include or be coupled to one or more electrodes, such as in communication with one or more sense amplifiers, such as to monitor electrical heart activity within a patient. Such devices can include one or more sensors, such as to monitor one or more patient physiological parameters. Other examples of medical devices can include implantable diagnostic devices, implantable drug delivery systems, or implantable devices with neural stimulation capability.
An example of a system and method for diagnosing and monitoring of congestive heart failure for use in automated patient care by comparing recorded physiological measures to at least one other recorded physiological measure to quantify a change in patient status is described in U.S. Pat. No. 6,811,537 to Bardy, entitled, “System and Method for Providing Diagnosis and Monitoring of Congestive Heart Failure for use in Automated Patient Care.”
An example of detecting myocardial ischemia by monitoring a time-wise sequential cascade of physiologic cardiovascular events corresponding to electrical sensor signals is described in U.S. patent application Ser. No. 11/426,835 to Wariar, et al., entitled, “Detection of Myocardial Isehemia from the Time Sequence of Implanted Sensor Measurements.”